Yesterday I completed the pirate chain for the first time ever, and tried to upgrade the Corroded Rapier I found along the way. House Deneith map shows the altar on top of the tower, but I could not find the way to it. Two stairways which encircle the tower on the right and on the left dead-end a bit below the top. The front door opens only for "Tide Turns quest". How do I get to the altar?
Or is the altar actually in the quest, like Shroud altars?